This invention of the Plottner Rotor Kite is considered by me to be a model rotor kite and most certainly in its larger possible sizes can not be considered to be a toy as I have observed is used in the name of some other rotating wing type apparatuses named in patent files. Even the rotors on this model rotor kite at times have a very high revolutions per minute and the tip speed of the 50 inch length rotors can be quite dangerous at the higher speeds so I envision it to be difficult to call this invention a toy.
I do believe this invention does fall into the category of a model rotor kite and therefore have given it that name description. There are many rotary wing devices in the patent listings and all of them must overcome the dissymmetry of lift problem that is inherent in a rotating rotor blade. That is the simple fact that any spinning rotor, whether it be on an autogiro that is moving down a runway and therefore has a relative wind to contend with, or if it is a rotor kite that is sitting on the ground ready for takeoff in a wind that is blowing at perhaps 10 miles per hour in velocity, has to contend with the problem of one half of the rotation of a particular rotor will always be going with the wind and the other half of the rotor will be going against the wind and this will create the dissymmetry of lift mentioned above. To overcome this most of the inventions of these kind of flying models use a teetering rotor design which allows the rotor to teeter much like a teeter-totter at a children's playground. This is the arrangement used on the Plottner Rotor Kite but with this invention two counter rotating rotors are used on a single mast and in addition to the teetering action of each rotor the counter revolving of the two rotors also adds to the overcoming of the dissymmetry of lift and adds considerably to the stableness of the complete unit.
Another inherent problem with any rotary wing propelled flyer is the problem of control and many other patents that I have examined claim flight with one control line, much as many ordinary kites are flown. I question whether any of these claims of flight with a single control line are valid except for very short flights of a second or so. I have had first hand experience with a product I purchased several years ago which has a patent number of U.S. Pat. No. 5,381,988. This was a very well made product with the outline of a helicopter fuselage in plastic with a very efficient plastic rotor of perhaps 12 inches in length attached to a metal mast at the top of the fuselage. The rotor on this unit spun up very well in even light winds of 6 miles per hour and it claimed to be able to be controlled with just one control line which was attached to its front center. I flew this model quite often on the beaches at Cape Hatteras where I have done much of my testing but the only time I ever had sustained flight was after I added my own design of two control lines. All of my flights with one control line basically ended in failure while with two lines the craft could be flown for many minutes and actually at times be landed safely. So the idea of control is of great importance for while we want the Plottner Rotor Kite to be completely controllable we also want it to be a challenge to fly and we believe that it is that with its special arrangement of the control lines.
Yet anther flaw in the designs I have studied is often the use of balsa wood in the makeup of the rotor blades. My experience with balsa rotor blades is that they are so dainty that the slightest kind of accident can destroy them completely. The rotor blades used on the Plottner Rotor Kite are made from sturdy yet reasonably light Poplar wood and very easily repaired in most cases with a few dabs of Elmer's glue. It also seems that most of these older patents have weighted rotor blades which means they have a weight someplace near the leading edge of each blade to bring its width wise balance to a point that is approximately 25 percent of the total width of the blade from the leading edge of the blade. We do not question that on full size man carrying rotor blades this is an absolute necessity. But we have found that we do not need this tedious building procedure on our Plottner Rotor Kite.